Severe statin-induced autoimmune myopathy successfully treated with intravenous immunoglobulin

Unveiling the Rare Complication: Statin-Induced Immune-Mediated Necrotizing Myopathy

BACKGROUND Statin-induced necrotizing autoimmune myopathy is an exceptionally rare yet severe complication of statin therapy that may develop in individuals at any time during their exposure to statins. The development of proximal muscle weakness, muscle pain, and elevated creatine kinase (CK) levels in patients while taking statins should prompt clinical consideration of statin-induced myopathy. The pathophysiology arises from the production of auto-antibodies, which target the 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase) enzyme, leading to the aggressive breakdown of myofibrils. CASE REPORT Here, we present a case of a 59-year-old woman with a medical history of dyslipidemia who developed anti-HMG-CoA reductase antibodies after taking atorvastatin. She came to the emergency department with complaints of severe proximal muscle weakness. The laboratory workup showed an elevated CK level up to 12 000 IU/L. Despite discontinuing atorvastatin, the patient's elevated CK levels persisted. The patient underwent a muscle biopsy, demonstrating myofibril necrosis. Serological analysis showed anti-HMG-CoA reductase antibodies in the patient's serum, which led to the diagnosis of immune-mediated necrotizing myopathy due to statins. The patient's statin therapy was promptly discontinued, and she was treated with a high dose of IV corticosteroids. After the patient's discharge, brief discontinuation of the corticosteroids resulted in CK elevation and a return of symptoms. This led to the second re-admission and restarting of corticosteroids until stabilization and discharge. CONCLUSIONS This case represents an important reminder for clinicians to recognize the possibility of statin-induced immune-mediated necrotizing myopathy in patients presenting with proximal muscle weakness while taking a statin, notwithstanding the rarity of this condition.

Statin-Induced Myositis with Concomitant Myocarditis

Statins are commonly prescribed medications that provide many significant cardiovascular benefits for both primary and secondary prevention in patients with and without coronary artery disease. Known adverse effects of these medications include varying degrees of muscle toxicity, including myalgia, myopathy, and rare cases of necrotizing myositis, hepatic dysfunction, and central nervous system changes. Despite known adverse effects, statins are rarely associated with myocarditis. Statins can cause skeletal muscle myopathy and myositis by upregulating HMG-CoA reductase (HMGCR) in muscle tissue, resulting in antibody-mediated inflammation. A similar proposed mechanism is likely possible within cardiac myocytes. We present a rare case of statin-induced necrotizing myositis with concomitant cardiac involvement. Severe skeletal muscle myositis was confirmed by lower extremity MRI and biopsy findings. In association, elevated and plateaued high-sensitivity troponin without evidence of cardiac ischemia warranted cardiac MRI, which further confirmed myocarditis due to inflammation within a non-vascular distribution. Given its rare presentation, the treatment for statin-induced cardiac toxicity is unclear; however, the patient in this case report was treated with pulse-dose intravenous steroids and indefinite discontinuation of statin medications.

Challenges in Treating Statin-Associated Necrotizing Myopathy

Myalgia and mild elevation in muscle enzymes are common side effects of statin therapy. While these symptoms are generally self-limited, in rare cases, statin use is associated with an immune-mediated necrotizing myopathy caused by development of autoantibodies against HMG-CoA reductase. The primary presenting symptom of this condition is progressive symmetric proximal weakness that does not abate or worsens even after cessation of statin therapy and is associated with markedly elevated creatine kinase (CK) levels. To date, no randomized controlled trials have been conducted to identify the most effective treatment for statin-associated autoimmune myopathy. Treatment recommendations involve a combination of steroids and immunosuppressive drugs. This single-center case series highlights the clinicopathologic features diagnostic for statin-associated autoimmune myopathy as well as treatment challenges for the patient population. The series highlights a range of potential presentations, from mildly symptomatic despite highly elevated CK, to severe muscle weakness including dysphagia. Multiple patients required several immunosuppressant medications as well as intravenous immunoglobulin (IVIG) to achieve disease control. In this case series, marked improvement was noted in several diabetic patients with IVIG.